1. Field of the Invention
The present invention relates to a substrate holder, an anodizing apparatus, a semiconductor processing system, and a method of processing or fabricating a substrate and, more particularly, to a substrate holder for holding a substrate to be anodized, an anodizing apparatus including the holder, a semiconductor processing system, and a method of processing or fabricating a substrate.
2. Description of the Related Art
Porous silicon was found by A. Uhlir and D. R. Turner during the course of researching electrolytic polishing of single-crystal silicon biased to a positive potential in an aqueous solution of hydrofluoric acid (to be abbreviated as HF hereinafter).
Thereafter, by focusing attention on a high reactivity of porous silicon, the application of porous silicon to a device isolation step requiring the formation of a thick insulator in the fabrication process of a silicon integrated circuit has been studied, and a complete isolation technique using a porous silicon oxide film (FIPOS: Full Isolation by Porous Oxidized Silicon) and the like have been developed (K. Imai, Solid State Electron 24, 159, 1981).
Also, an applied technique to a direct adhesion technique by which a silicon epitaxial layer grown on a porous silicon substrate is adhered on an amorphous substrate or a single-crystal silicon substrate via an oxide film has been developed recently (Japanese Patent Laid-Open No. 5-21338).
As another application, porous silicon which emits light by itself has attracted attention as so-called photoluminescence and electroluminescence materials (Japanese Patent Laid-Open No. 6-338631).
FIG. 17 is a view showing the arrangement of an apparatus for fabricating porous silicon by anodizing a silicon substrate. In this apparatus, the lower surface of a silicon substrate 1701 is brought into tight contact with a metal electrode 1702, and an anodizing bath 1705 is placed on the silicon substrate 1701 such that the peripheral portion on the upper surface of the silicon substrate 1701 is sealed by, e.g., an O-ring 1704. The bath is filled with an HF solution 1703, and a counterelectrode 1706 is arranged in the bath so as to oppose the silicon substrate 1701. The silicon substrate 1701 is anodized by applying a DC voltage by using the counterelectrode 1706 as a negative electrode and the metal electrode 1702 as a positive electrode.
This method has two major drawbacks. One drawback is that the silicon substrate 1701 is contaminated with the metal because the lower surface of the silicon substrate 1701 is in direct contact with the metal. The other drawback is that a region to be anodized on the surface of the silicon substrate 1701 is only a portion contacting the HF solution, so porous silicon is formed only inside the O-ring 1704.
FIG. 18 is a view showing the arrangement of an anodizing apparatus (Japanese Patent Laid-Open No. 60-94737) developed to solve the above problems. In this anodizing apparatus, HF-resistant Teflon anodizing baths 1802a and 1802b (Teflon is a tradename of Du Pont de Nemours and Co. Inc., U.S.A) are so arranged as to sandwich a silicon substrate 1801. Platinum electrodes 1803a and 1803b are arranged in the anodizing baths 1802a and 1802b, respectively.
The anodizing baths 1802a and 1802b have grooves in side walls contacting the silicon substrate 1801, and O-rings 1804a and 1804b made from fluorine rubber are fitted in these grooves. The anodizing baths 1802a and 1802b and the silicon substrate 1801 are sealed by these O-rings 1804a and 1804b, respectively. The anodizing baths 1802a and 1802b thus sealed are filled with HF solutions 1805a and 1805b, respectively.
In these anodizing baths, as the silicon substrate does not directly contact the metal electrodes; the possibility of the silicon substrate being contaminated by the metal electrodes is low. However, the front and rear surfaces of the silicon substrate to be anodized are sealed by the O-rings. Accordingly, the problem that an unanodized portion remains in the peripheral region of the surfaces of the silicon substrate still remains unsolved. Also, since the silicon substrate to be processed is directly incorporated into and integrated with the anodizing baths, it is impossible to rapidly exchange the silicon substrates.
In consideration of the above problems, an anodizing apparatus which supports a beveling region of a silicon substrate was developed (Japanese Patent Laid-Open No. 5-198556). This anodizing apparatus can prevent contamination from a metal electrode and anodize the entire region of the surface of a silicon substrate. Also, this anodizing apparatus fixes a wafer to be processed in an anodizing bath in two steps in which the wafer is fixed by a holder and the holder is then fixed in the anodizing bath. This greatly improves the operability compared to the conventional apparatus in which a wafer is directly fixed in an anodizing bath to form a part of the anodizing bath.
The anodizing apparatus described in Japanese Patent Laid-Open No. 5-198556 is an extremely practical apparatus which produces almost no metal contamination and can anodize the entire region of the substrate surface.
It is, however, being desired to develop an anodizing apparatus with a higher productivity. For example, when it is necessary to process a large number of types of substrates different in a diameter (e.g., an inch size) or a shape (e.g., an orientation flat or a notch), the anodizing apparatus described in Japanese Patent Laid-Open No. 5-198556 must be equipped with dedicated holders for the individual substrates.
Additionally, in incorporating a substrate into a holder, it is necessary to first match the center of the wafer with the center of a seal surface, match a special-shape portion such as an orientation flat with a corresponding portion of the holder, and then fix the wafer by pushing the seal surface against the periphery of the wafer. Since a considerable press force is required to fix the wafer, screws, for example, are used in the fixation.
The present invention has been made in consideration of the above situation, and has as its object to increase the efficiency of anodization by improving a substrate supporting method.
An anodizing apparatus according to one embodiment of the present invention is an anodizing apparatus for anodizing a substrate in an electrolytic solution, comprising a pair of opposing electrodes, and a holding unit for holding a portion of one surface of a substrate by suction between the electrodes.
In the above anodizing apparatus, a main body of the holding unit preferably has an opening through which an electrolytic solution is brought into contact with a rear surface of the held substrate.
In the above anodizing apparatus, it is preferable that the holding unit comprise a substantially annular suction member for holding a substrate by suction, and the suction member be arranged along an inside of an outer peripheral portion of a substrate to be held.
In the above anodizing apparatus, the suction member preferably comprises two O-rings constituting a double structure and a suction hole for holding a substrate by suction by reducing a pressure in a space between the two O-rings.
In the above anodizing apparatus, the suction member preferably comprises a suction pad having a concave sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above anodizing apparatus, the suction member preferably comprises a suction pad having a U sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above anodizing apparatus, the suction member preferably comprises a suction pad having a flat contact portion to be brought into contact with a rear surface of a substrate to be held and a substantially annular groove in a surface of the contact portion, and a suction hole for holding a substrate by suction by reducing a pressure in a space in the groove of the suction pad.
In the above-anodizing apparatus, the suction member is preferably brought into tight contact with a substrate to be held so as to prevent an electrolytic solution on a front surface of the substrate from moving to a rear surface of the substrate.
The above anodizing apparatus preferably comprises a plurality of the holding units.
A substrate holder according to another embodiment of the present invention is a substrate holder for holding a substrate to be anodized in an electrolytic solution, wherein a main body comprises a suction member for holding a portion of one surface of a substrate by suction, and an opening through which an electrolytic solution is brought into contact with a rear surface of the held substrate.
In the above substrate holder, the suction member is preferably arranged along an inside of an outer peripheral portion of the held substrate.
In the above substrate holder, the suction member preferably comprises two O-rings constituting a double structure and a suction hole for holding a substrate by suction by reducing a pressure in a space between the two O-rings.
In the above substrate holder, the suction member preferably comprises a suction pad having a concave sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above substrate holder, the suction member preferably comprises a suction pad having a U sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above substrate holder, the suction member preferably comprises a suction pad having a flat contact portion to be brought into contact with a rear surface of a substrate to be held and a substantially annular groove in a surface of the contact portion, and a suction hole for holding a substrate by suction by reducing a pressure in a space in the groove of the suction pad.
In the above substrate holder, the suction member is preferably brought into tight contact with a substrate to be held so as to prevent an electrolytic solution on a front surface of the substrate from moving to a rear surface of the substrate.
An anodizing system according to still another embodiment of the present invention comprises the above anodizing apparatus, a cleaning apparatus for cleaning an anodized substrate, a drying apparatus for drying the cleaned substrate, and a convey apparatus for conveying the substrate between the apparatuses.
In the above anodizing system, it is preferable that the drying apparatus comprise a receiving unit for receiving the cleaned substrate, and the anodizing apparatus, the cleaning apparatus, and the receiving unit be substantially arranged in a straight line.
In the above anodizing system, it is preferable that the drying apparatus comprise a receiving unit for receiving the cleaned substrate, the anodizing apparatus, the cleaning apparatus, and the receiving unit be substantially arranged in a straight line, and the convey apparatus convey the substrate such that surfaces of the substrate are parallel to a direction perpendicular to the straight line.
In the above anodizing system, the convey apparatus preferably comprises a first convey robot for conveying the substrate from the anodizing apparatus to the cleaning apparatus, and a second convey robot for conveying a carrier containing the substrate from the cleaning apparatus to the receiving unit of the drying apparatus.
In the above anodizing system, each of the first and second convey robots preferably has only a first driving shaft for moving the substrate or the carrier to a portion above each apparatus and a second driving shaft for moving the substrate or the carrier along the straight line, as driving shafts for conveying the substrate or the carrier.
The above anodizing system preferably further comprises a filter apparatus for purifying an electrolytic solution in the anodizing apparatus.
In the above anodizing system, the filter apparatus preferably comprises a tank for storing an electrolytic solution and a circulating mechanism for supplying the electrolytic solution stored in the tank into the anodizing apparatus and returning an electrolytic solution overflowing from the anodizing apparatus to the tank.
A semiconductor processing system according to still another embodiment of the present invention is a semiconductor processing system for processing a semiconductor substrate, comprising a cleaning apparatus for cleaning the semiconductor substrate, a drying apparatus for drying the semiconductor substrate cleaned by the cleaning apparatus, and a convey apparatus for conveying the semiconductor substrate from a preceding step of the cleaning to the cleaning apparatus and from the cleaning apparatus to the drying apparatus, wherein the drying apparatus comprises a receiving unit for receiving the cleaned semiconductor substrate, the cleaning apparatus and the receiving unit are substantially arranged in a straight line, and the convey apparatus conveys the semiconductor substrate such that surfaces of the semiconductor substrate are parallel to a direction perpendicular to the straight line.
In the above semiconductor processing system, the convey apparatus preferably comprises a first convey robot for conveying the substrate to the cleaning apparatus, and a second convey robot for conveying the substrate contained in a carrier from the cleaning apparatus to the receiving unit of the drying apparatus.
In the above semiconductor processing system, each of the first and second convey robots preferably has only a first driving shaft for moving the substrate or the carrier to a portion above each apparatus and a second driving shaft for moving the substrate or the carrier along the straight line, as driving shafts for conveying the substrate or the carrier.
A substrate fabrication method according to still another embodiment of the present invention comprises the steps of holding a portion of one surface of a substrate by suction between a pair of opposing electrodes, and anodizing the substrate by applying a voltage between the electrodes with an electrolytic solution being filled.
An anodizing apparatus according to still another embodiment of the present invention is an anodizing apparatus for anodizing a substrate in an electrolytic solution, comprising a pair of opposing electrodes, and a holding unit for holding one surface of a substrate by suction between the electrodes, wherein the holding unit comprises a plurality of substantially annular suction members for holding a substrate by suction, the suction members differing in size.
In the above anodizing apparatus, it is preferable that a main body of the holding unit have a substantially circular opening, the opening have at least one substantially annular intermediate surface between front and rear surfaces of the main body, the front surface of the main body and the intermediate surface be so arranged as to form a stepwise shape, and the front surface of the main body and the intermediate surface have the suction members differing in size.
In the above anodizing apparatus, each of the suction members preferably comprises two O-rings constituting a double structure and a suction hole for holding a substrate by suction by reducing a pressure in a space between the two O-rings.
In the above anodizing apparatus, each of the suction members preferably comprises a suction pad having a concave sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above anodizing apparatus, each of the suction members preferably comprises a suction pad having a U sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above anodizing apparatus, each of the suction members preferably comprises a suction pad having a flat contact portion to be brought into contact with a rear surface of a substrate to be held and a substantially annular groove in a surface of the contact portion, and a suction hole for holding a substrate by suction by reducing a pressure in a space in the groove of the suction pad.
The above anodizing apparatus preferably comprises a plurality of the holding units.
The above anodizing apparatus preferably further comprises a control unit for independently controlling substrate suction operations by the suction members.
In the above anodizing apparatus, a step difference of the stepwise shape formed by the front surface of the main body and the intermediate surface is preferably at least 5 mm.
A substrate holder according to still another embodiment of the present invention is a substrate holder for holding a substrate to be anodized in an electrolytic solution, comprising a main body having a plurality of substantially annular suction members for holding a substrate, the suction members differing in size.
In the above substrate holder, it is preferable that the main body have a substantially circular opening, the opening have at least one substantially annular intermediate surface between front and rear surfaces of the main body, the front surface of the main body and the intermediate surface be so arranged as to form a stepwise shape, and the front surface of the main body and the intermediate surface have the suction members differing in size.
In the above substrate holder, each of the suction members preferably comprises two O-rings constituting a double structure and a suction hole for holding a substrate by suction by reducing a pressure in a space between the two O-rings.
In the above substrate holder, each of the suction members preferably comprises a suction pad having a concave sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above substrate holder, each of the suction members preferably comprises a suction pad having a U sectional shape and a suction hole for holding a substrate by suction by reducing a pressure in a space in a valley of the suction pad.
In the above substrate holder, each of the suction members preferably comprises a suction pad having a flat contact portion to be brought into contact with a rear surface of a substrate to be held and a substantially annular groove in a surface of the contact portion, and a suction hole for holding a substrate by suction by reducing a pressure in a space in the groove of the suction pad.
In the above substrate holder, a step difference of the stepwise shape formed by the front surface of the main body and the intermediate surface is preferably at least 5 mm.
A porous substrate fabrication method according to still another embodiment of the present invention anodizes a substrate by using the above anodizing apparatus.
An anodizing system according to still another embodiment of the present invention comprises the above anodizing apparatus, a cleaning apparatus for cleaning an anodized substrate, a drying apparatus for drying the cleaned substrate, and a convey apparatus for conveying the substrate between the apparatuses.
In the above anodizing system, it is preferable that the drying apparatus comprise a receiving unit for receiving the cleaned substrate, and the anodizing apparatus, the cleaning apparatus, and the receiving unit be substantially arranged in a straight line.
In the above anodizing system, it is preferable that the drying apparatus comprise a receiving unit for receiving the cleaned substrate, the anodizing apparatus, the cleaning apparatus, and the receiving unit be substantially arranged in a straight line, and the convey apparatus convey the substrate such that surfaces of the substrate are parallel to a direction perpendicular to the straight line.
In the above anodizing system, the convey apparatus preferably comprises a first robot for conveying the substrate from the anodizing apparatus to the cleaning apparatus, and a second robot for conveying a carrier containing the substrate from the cleaning apparatus to the receiving unit of the drying apparatus.
In the above anodizing system, each of the first and second robots preferably has only a first driving shaft for moving the substrate or the carrier to a portion above each apparatus and a second driving shaft for moving the substrate or the carrier along the straight line, as driving shafts for conveying the substrate or the carrier.
The above anodizing system is suited to fabricate a substrate having a porous layer by anodizing the substrate.
A substrate according to still another embodiment of the present invention has a porous layer obtained by holding a portion of one surface of the substrate by suction between a pair of opposing electrodes, and anodizing the substrate by applying a voltage between the electrodes with an electrolytic solution being filled.
A semiconductor substrate fabrication method according to still another embodiment of the present invention is a method of fabricating a semiconductor substrate by using two substrates, comprising the steps of holding a portion of one surface of a semiconductor substrate by suction between a pair of opposing electrodes and anodizing the semiconductor substrate by applying a voltage between the electrodes with an electrolytic solution being filled, thereby forming a porous layer on one surface of the semiconductor substrate, forming a single-crystal silicon layer on the porous layer of the semiconductor substrate, adhering another substrate to the single-crystal silicon layer of the semiconductor substrate, and separating the two adhered substrates from the porous layer.
A substrate fabrication method according to still another embodiment of the present invention is a method is of fabricating a substrate having a porous layer, comprising the steps of dipping a substrate into an anodizing bath filled with an electrolytic solution and holding a portion of one surface of the substrate by suction by a suction member between the electrodes, anodizing the substrate by applying a voltage between the electrodes to form a porous layer on one surface of the substrate, removing the substrate on which the porous layer is formed from the anodizing bath and dipping the substrate into a cleaning bath to clean the substrate, and removing the completely cleaned substrate from the cleaning bath, and conveying the substrate to a drying apparatus to dry the substrate.
In the above substrate fabrication method, the anodizing bath, the cleaning bath, and the drying apparatus are preferably substantially arranged in a straight line when viewed from above, thereby conveying the substrate such that a substrate convey path from the anodizing bath to the cleaning bath and a substrate convey path from the cleaning bath to the drying apparatus are substantially arranged in a straight line when viewed from above.
It is preferable that the above substrate fabrication method further comprise the step of conveying the dried substrate from the drying apparatus to an unloader, and the substrate be conveyed from the cleaning bath to the drying apparatus and from the drying apparatus to the unloader by a single robot.
The above substrate fabrication method preferably further comprises the step of drying the robot after the robot conveys the substrate from the cleaning bath to the drying apparatus and before the robot conveys the substrate from the drying apparatus to the unloader.
In the above substrate fabrication method, the step of drying the robot is preferably performed on the straight line.
A substrate processing method according to still another embodiment of the present invention comprises the steps of dipping a substrate into a processing bath filled with a chemical processing solution and chemically processing the substrate, removing the chemically processed substrate from the processing bath and dipping the substrate into a cleaning bath to clean the substrate, and removing the completely cleaned substrate from the cleaning bath and conveying the substrate to a drying apparatus to dry the substrate, wherein the processing bath, the cleaning bath, and the drying apparatus are substantially arranged in a straight line when viewed from above, thereby conveying the substrate such that a substrate convey path from the processing bath to the cleaning bath and a substrate convey path from the cleaning bath to the drying apparatus are substantially arranged in a straight line when viewed from above, and that surfaces of the substrate point in a direction perpendicular to the straight line.
It is preferable that the above substrate processing method further comprise the step of conveying the dried substrate from the drying apparatus to an unloader, and the substrate be conveyed from the cleaning bath to the drying apparatus and from the drying apparatus to the unloader by a single robot.
The above substrate processing method preferably further comprises the step of drying the robot after the robot conveys the substrate from the cleaning bath to the drying apparatus and before the robot conveys the substrate from the drying apparatus to the unloader.
A substrate processing system according to still another embodiment of the present invention comprises a processing bath for chemically processing a substrate, a cleaning bath for cleaning the substrate chemically processed by the processing bath, a drying apparatus for drying the substrate cleaned by the cleaning bath, and a convey apparatus for conveying the substrate from the processing bath to the cleaning bath and from the cleaning bath to the drying apparatus, wherein the processing bath, the cleaning bath, and the drying apparatus are substantially arranged in a straight line when viewed from above, and the convey apparatus conveys the substrate such that surfaces of the substrate point in a direction perpendicular to the straight line.
In the above substrate processing system, the convey apparatus preferably comprises a first convey robot for conveying the substrate from the processing bath to the cleaning bath, and a second convey robot for conveying the substrate from the cleaning bath to the drying apparatus and from the drying apparatus to an unloader.
The above substrate processing system preferably further comprises a second drying apparatus for drying the second convey robot after the second convey robot conveys the substrate from the cleaning bath to the drying apparatus and before the second convey robot conveys the substrate from the drying apparatus to the unloader.